Witnesses say two people have been killed and more than a dozen injured in a series of grenade blasts in the Burundian capital.

Two of the explosions happened in an open market on Monday in the Ngagara area of Bujumbura, killing at least two. Two other grenades exploded in the center of Bujumbura, injuring 11 people. Another explosion happened in the Buyenzi area, wounding at least three people.

The witnesses spoke on the condition of anonymity, citing concerns for their safety.

Bujumbura has been plagued by violence since last April, when the president announced he would seek an ultimately successful third term in office. Gunfire and loud explosions are frequently heard here.

According to the U.N., hundreds of people have been killed in the unrest.